a. Field of the Invention
This invention is directed to an apparatus for in-line, continuous stacking of paper signatures. Two or more horizontally disposed batch forks include integral, pivoting fingers which separate the incoming shingles by depressing the leading edge of the last shingle in the batch/stack. The leading edge of the next shingle rides over the top of the integral, pivoting fingers to begin the next batch/stack on the batch forks.
Several different batch/stack handling systems are contemplated, depending on the speed required for the system. In one embodiment, batch/stack handling apparatus is provided so that a partial stack is formed and held while a first stack is being delivered to a downstream conveyor system. When the first stack has been delivered to the conveyor, the handling apparatus returns to its original position to receive the partial stack. When the intermediate stack is completed, it is delivered to the downstream conveyor system. While the intermediate stack is being completed, the intermediate stack forks are returning to their original starting position; the cycle repeats continuously.
In another embodiment in which speed of stacking is not as critical, the intermediate stacking apparatus is eliminated. It is only necessary then to provide means for delivering the upper stack supported on the batch forks, and the lower stack which has been diverted below the batch forks to the downstream conveyor system in an alternating, coordinated flow.
b. Description of the Related Art
There are a number of systems described in the prior art for stacking signatures. U.S. Pat. No. 3,543,651 to Donahue et al describes a machine which inverts the line of incoming shingles and inserts the papers into the bottom of a stack.
The flow of papers is interrupted to form a gap in the line in response to a signal from a photoelectric cell counter. The gap is sensed by a first switch, which then causes the first conveyor to resume operation. When the gap reaches a second switch, a limit stop is activated to release the stack to the conveyor system. The stack then moves over a third switch, causing the limit stop to be extended through the gap to start the next stack. The Donahue et al system is really not continuous, and is not adapted to high speed stacking.
Cogswell et al, U.S. Pat. No. 4,130,207, piles a continuous stream of "booklets", bottom up. At a predetermined stack size, the stack is ejected from the apparatus without stopping delivery of the continuous stream of booklets, which are accumulated in a temporary holding stack. The temporary holding stack is depleted at a rate faster than it is formed, following ejection of the other stack. Cogswell et al is directed to top stacking apparatus, but each booklet is delivered to the stack through the nip between a drive wheel and a weighted wheel which receives the booklets from a conveyor. Ejector fingers transfer the stacked booklets horizontally to a downstream location. It is believed that the stacking speed is limited by the drive wheel stack feeding system, and that a potential for misfeeds to the stack exists as well as clogging of the temporary stack which forms while the first stack is being moved to the downstream stack conveyer, and while the downstream stacker is filling.
Chandhoke et al, U.S. Pat. No. 4,541,763, describes a device for stacking signatures which includes an interceptor for initiating the formation of a stack, and which transfers the partially formed stack from the interceptor to the main member. A "gapper" having a retarder roller assembly separates the successive shingles into predetermined quantities for stacking. The interceptor only responds to a "gap" in the shingles created by the retarder roller assembly, and does not initiate separation of the stacks.
Voss et al, U.S. Pat. No. 4,610,593, describes a conveyor/stacker device which includes an upper and two lower belts. The upper belt can be shifted over to one or the other of the two lower belts to unload and convey a completed stack. Vijuk, U.S. Pat. No. 4,616,515, disclosed an automatic stacking and folding apparatus which receives, stacks and folds shingled sheets from a printing press. The sheets are counted by photocells. The sheets are first automatically aligned, folded and then stacked. The stacking apparatus includes retractable stop fingers 54 (FIG. 15). The stack is built up from the bottom to about 50 signatures, and is then conveyed away by conveyor belts 58. A detailed description appears at Column 9 of the patent specification.
U.S. Pat. No. 4,772,003 issued to Nobuta et al describes a stacking system in which signatures are loaded vertically from above. A laser beam is used to count the signatures, and a dividing plate 39 separates the succeeding stream 20 of signatures at the accumulating plate 41. See Column 12 of the specification and FIGS. 8 and 9 of the patent. The dividing plate appears to have only one function, that is, to hold up the stream 20 until the dividing plate is retracted. The dividing plate does not appear to divert the flow of signatures.